CINCINNATI, Ohio (Kyodo) -- Japan's Naomi Osaka was knocked out of the women's singles tournament at the Western & Southern Open after suffering a first-round defeat by Greece's Maria Sakkari on Tuesday.
Despite slamming seven aces against her opponent, Osaka was unable to capitalize on her opponent's four double faults and eventually succumbed 6-3, 7-6(8) against the No. 31 Sakkari's superior service game.
The 20-year-old Japanese led briefly in the first set but lost momentum in its second half. In a second set lasting more than an hour, Osaka had three set-point opportunities in a hard-fought tiebreaker but lost three straight points to fall.
Osaka, currently 19th in the world, also made a first-round exit at last week's Rogers Cup after she was unable to recover losing a tiebreaker in her first set against Spain's Carla Suarez Navarro.
In the women's doubles, Japan's Shuko Aoyama and partner Lidziya Marozava of Belarus defeated Estonian Anett Kontaveit and Australian Daria Gavrilova 6-4, 6-0 to advance to the second round.
The hardcourt tournament at Lindner Family Tennis Center is one of five Premier 5 events in the WTA season and serves as the final warm-up for the upcoming U.S. Open, the last Grand Slam of the year.